1. Field of the Invention
The invention relates to a process for reprocessing crushed organic waste products, in particular rubber waste such as worn car tires, by pyrolysis cited in the preamble of claim 1 and to apparatus for carrying out this process.
2. Description of the Related Art
There is a continuous increase in organic waste matter produced, in particular worn car tires and it has reached such a level that depositing of this waste matter is no longer possible to the extent required. The depositing of such matter, moreover, causes problems, since under unfavourable conditions contamination of the groundwater may occur as a result of a leakage of the waste matter which could possibly lead to irreparable damage. A further disadvantage of depositing such matter is that it sometimes includes valuable materials which could be converted into valuable substances by suitable recycling and thus returned to the raw material cycle.
For this reason attempts have been made for some time to decompose this waste matter in suitable pyrolysis plants. The combustible matter (solid, liquid and gaseous mixtures) liberated in the pyrolysis has been used in some cases, either in part or completely, to produce, through combustion, the heat needed for the pyrolysis. Such processes are disclosed, for example, in DE-A-2 219 227, FR-2,288,139, EP-A-0024 250 and DE-A-3 614 048.
Attempts have also been made to bind accompanying substances frequently occurring in this waste matter, such as sulfur contained, for example, in car tires, for the purpose of vulcanization, chlorine or toxic metals, e.g., antimony, vanadium or lead, in the solids accompanying the reaction so that they are not able to escape into the atmosphere and provision of expensive purification processes for the volatile constituents are avoided. EP-A-0 070 789 discloses a process in which these elements are absorbed by chemical reaction in a salt bath of alkali and alkaline earth hydroxides and oxides used for the pyrolysis.
Another possibility for carrying out the process is to produce solid, liquid and gaseous organic basic materials in the pyrolysis. These chemical mixtures may either be used for heat production by means of combustion or for chemical synthesis after a further reprocessing of the mixtures, e.g., by means of a distillation. Unsaturated hydrocarbons, such as alkenes and aromatic substances, are particularly valuable since they may be used directly for chemical syntheses.
Carbon black which is also produced in these processes is, for example, used as an elastomeric filler, in particular in car tires, as pigment in paints, lacquers, plastics materials and in electrophotographic processes or as electrodes in batteries. EP-A-025 319 discloses a process in which the temperatures set for the pyrolysis in pyrolysis plants connected in series are different and the product mixtures produced in the individual parts are removed separately. This reduces the costs for the necessary reprocessing of the product mixtures.
A process is described in FR-2,288,139, in which the pyrolysis of worn car tires is carried out under the exclusion of air. Here the process is carried out at reduced pressure and, in one embodiment disclosed, while feeding overheated water vapor into the reactor. The resultant product gas, however, is contaminated by the water vapor and has to be removed again in a purification process.
All the known processes and apparatus for carrying out the process have the common disadvantage that the resultant product mixture is of a low grade and only contains relatively small amounts of high-grade fractions such as gasoline and kerosene. In most cases, depending on the reaction process, predominantly higher amounts of gaseous products, such as methane and ethane, are obtained. The carbon produced is, moreover, mostly of a lower quality.
The invention has the object of achieving, in a process of the kind mentioned above, as complete as possible a conversion of waste matter into raw materials which are reusable and as pure as possible.